feat(swarm): Add direct swarm interaction delivery for likes, reposts, and unreosts

- Add swarm post handling to like endpoint with direct delivery to origin node
- Add swarm post handling to repost endpoint with direct delivery to origin node
- Add new unrepost endpoint for removing reposts from swarm posts
- Implement deliverSwarmUnrepost function in interactions library
- Extract swarm domain and post ID validation for all interaction types
- Return appropriate error responses for invalid swarm post IDs
- Log successful swarm interaction deliveries for debugging
- Improve separation between local post and swarm post handling logic
- Enable federated users to interact with remote swarm posts directly without local caching

src/app/api/swarm/interactions/unrepost/route.ts

@@ -0,0 +1,67 @@
+/**
+ * Swarm Unrepost Endpoint
+ * 
+ * POST: Receive an unrepost from another swarm node
+ */
+
+import { NextRequest, NextResponse } from 'next/server';
+import { db, posts } from '@/db';
+import { eq } from 'drizzle-orm';
+import { z } from 'zod';
+
+const swarmUnrepostSchema = z.object({
+  postId: z.string().uuid(),
+  unrepost: z.object({
+    actorHandle: z.string(),
+    actorNodeDomain: z.string(),
+    interactionId: z.string(),
+    timestamp: z.string(),
+  }),
+});
+
+/**
+ * POST /api/swarm/interactions/unrepost
+ * 
+ * Receives an unrepost from another swarm node.
+ */
+export async function POST(request: NextRequest) {
+  try {
+    if (!db) {
+      return NextResponse.json({ error: 'Database not available' }, { status: 503 });
+    }
+
+    const body = await request.json();
+    const data = swarmUnrepostSchema.parse(body);
+
+    // Find the target post
+    const post = await db.query.posts.findFirst({
+      where: eq(posts.id, data.postId),
+    });
+
+    if (!post) {
+      return NextResponse.json({ error: 'Post not found' }, { status: 404 });
+    }
+
+    if (post.isRemoved) {
+      return NextResponse.json({ error: 'Post not found' }, { status: 404 });
+    }
+
+    // Decrement repost count
+    await db.update(posts)
+      .set({ repostsCount: Math.max(0, post.repostsCount - 1) })
+      .where(eq(posts.id, data.postId));
+
+    console.log(`[Swarm] Received unrepost from ${data.unrepost.actorHandle}@${data.unrepost.actorNodeDomain} on post ${data.postId}`);
+
+    return NextResponse.json({
+      success: true,
+      message: 'Unrepost received',
+    });
+  } catch (error) {
+    if (error instanceof z.ZodError) {
+      return NextResponse.json({ error: 'Invalid request', details: error.issues }, { status: 400 });
+    }
+    console.error('[Swarm] Unrepost error:', error);
+    return NextResponse.json({ error: 'Failed to process unrepost' }, { status: 500 });
+  }
+}